Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Changes in accumulated other comprehensive income (loss) by component
Beginning balance		$ 5,348,705	$ 5,135,730
Ending balance		5,553,188	5,348,705
Pension and Other Postretirement Benefits
Changes in accumulated other comprehensive income (loss) by component
Beginning balance		(45,997)	(42,440)
OCI (loss) before reclassifications		(14,041)	102
Amounts reclassified from accumulated other comprehensive loss		3,516	4,295
Reclassification of income tax effect related to tax reform			(7,954)
Ending balance		(56,522)	(45,997)
Derivative Instruments
Changes in accumulated other comprehensive income (loss) by component
Beginning balance		(1,711)	(2,562)
OCI (loss) before reclassifications		0	(78)
Amounts reclassified from accumulated other comprehensive loss		1,137	1,527
Reclassification of income tax effect related to tax reform			(598)
Ending balance		(574)	(1,711)
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss) by component
Beginning balance		(47,708)	(45,002)
OCI (loss) before reclassifications		(14,041)	24
Amounts reclassified from accumulated other comprehensive loss		4,653	5,822
Reclassification of income tax effect related to tax reform	[1]		(8,552)
Ending balance		(57,096)	(47,708)
ARIZONA PUBLIC SERVICE COMPANY
Changes in accumulated other comprehensive income (loss) by component
Beginning balance		5,786,797	5,385,869
Ending balance		5,998,803	5,786,797
ARIZONA PUBLIC SERVICE COMPANY | Pension and Other Postretirement Benefits
Changes in accumulated other comprehensive income (loss) by component
Beginning balance		(25,396)	(24,421)
OCI (loss) before reclassifications		(12,572)	(326)
Amounts reclassified from accumulated other comprehensive loss		3,020	3,791
Reclassification of income tax effect related to tax reform			(4,440)
Ending balance		(34,948)	(25,396)
ARIZONA PUBLIC SERVICE COMPANY | Derivative Instruments
Changes in accumulated other comprehensive income (loss) by component
Beginning balance		(1,711)	(2,562)
OCI (loss) before reclassifications		0	(78)
Amounts reclassified from accumulated other comprehensive loss		1,137	1,527
Reclassification of income tax effect related to tax reform			(598)
Ending balance		(574)	(1,711)
ARIZONA PUBLIC SERVICE COMPANY | Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss) by component
Beginning balance		(27,107)	(26,983)
OCI (loss) before reclassifications		(12,572)	(404)
Amounts reclassified from accumulated other comprehensive loss		4,157	5,318
Reclassification of income tax effect related to tax reform	[2]		(5,038)
Ending balance		$ (35,522)	$ (27,107)

[1] In 2018, the Company adopted new accounting guidance and elected to reclassify income tax effects of the Tax Cuts and Jobs Act of 2017 (the "Tax Act") on items within accumulated other comprehensive income to retained earnings.

[2] In 2018, the Company adopted new accounting guidance and elected to reclassify income tax effects of the Tax Act on items within accumulated other comprehensive income to retained earnings.